The Transgenic Mouse/ES Cell subcore is a new support laboratory that is jointly administered by the DRTC and the Vanderbilt Cancer Center. The objective of this subcore is to assist investigators in generating germline-altered mice. These animals provide useful models for the study of diabetes and other diseases. Two key services are offered: the generation of transgenic mice by the microinjection of DNA and the production of chimeric mice by the microinjection of embryonic stem (ES) cells. Personnel of this subcore provide consultation in the generation and maintenance of transgenic mice. The subcore has been in operation for over a year and a half and has produced over 100 transgenic founder animals by the pronuclear microinjection of DNA. It has also aided investigators in performing gene knockout experiments by generating chimeric mice. An ES cell laboratory that will assist investigators in the performance of gene knockout experiments is being established as part of this subcore. This subcore met with high user approval in a presubmission review of our service facilities. Nine DRTC investigators intend to use this facility in 1995-96 for either pronuclear DNA microinjections or for embryonic stem cell injections into blastocysts.